Hindawi Publishing Corporation
Journal of Inequalities and Applications
Volume 2010, Article ID 915739, 13 pages
doi:10.1155/2010/915739
Research Article
Existence of Solutions and Nonnegative
Solutions for Prescribed Variable Exponent Mean
Curvature Impulsive System Initialized Boundary
Value Problems
Guizhen Zhi,1 Liang Zhao,2 Guangxia Chen,3
Xiaopin Liu,1 and Qihu Zhang1, 4
1
Department of Mathematics and Information Science, Zhengzhou University of Light Industry,
Zhengzhou, Henan 450002, China
2
Academic Administration, Henan Institute of Science and Technology, Xinxiang, Henan 453003, China
3
School of Mathematics and Informatics, Henan Polytechnic University, Jiaozuo, Henan 454003, China
4
School of Mathematics and Statistics, Huazhong Normal University, Wuhan, Hubei 430079, China
Correspondence should be addressed to Qihu Zhang, zhangqh1999@yahoo.com.cn
Received 10 May 2009; Accepted 23 January 2010
Academic Editor: Ondřej Dosly
Copyright q 2010 Guizhen Zhi et al. This is an open access article distributed under the Creative
Commons Attribution License, which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
This paper investigates the existence of solutions and nonnegative solutions for prescribed variable
exponent mean curvature impulsive system initialized boundary value problems. The proof of our
main result is based upon Leray-Schauder’s degree. The sufficient conditions for the existence of
solutions and nonnegative solutions have been given.
1. Introduction
The theory of impulsive differential equations describes processes which experience a
sudden change of their state at certain moments. On the Laplacian impulsive differential
equations boundary value problems, there are many results see 1–5. Because of the
nonlinearity of p-Laplacian, the results about p-Laplacian impulsive differential equations
boundary value problems are rare see 6. In 7, 8, the authors discussed the existence
of solutions of pr-Laplacian system impulsive boundary value problems. Recently, the
existence and asymptotic behavior of solutions of curvature equations have been studied
extensively see 9–15. In 16, the authors generalized the usual mean curvature systems
to variable exponent mean curvature systems. In this paper, we consider the existence of
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Journal of Inequalities and Applications
solutions and nonnegative solutions for the prescribed variable exponent mean curvature
system
− ϕ r, u f r, u, u 0,
1.1
r ∈ 0, T , r /
ri ,
where u : 0, T → RN , with the following impulsive initialized boundary value conditions
lim ur − lim− ur Ai
r → ri
r → ri
lim ur, lim− u r ,
r → ri−
lim ϕ r, u r − lim− ϕ r, u r Bi
r → ri
r → ri
1.2
r → ri
i 1, . . . , k,
lim ur, lim− u r ,
r → ri−
r → ri
i 1, . . . , k,
u 0 u0 0,
1.3
1.4
where
|x|pr−1 x
1/qr ,
1 |x|qrpr
ϕr, x ∀r ∈ 0, T , x ∈ RN ,
1.5
p, q ∈ C0, T , R are absolutely continuous, where p, q satisfy pr ≥ 1, qr ≥ 1,
−ϕr, u is called the variable exponent mean curvature operator, 0 < r1 < r2 < · · · <
rk < T and Ai , Bi ∈ CRN × RN , RN .
For any v ∈ RN , vj will denote the jth component of v; the inner product in RN will be
denoted by ·, ·; | · | will denote the absolute value and the Euclidean norm on RN . Denote
that J 0, T , J 0, T \ {r0 , r1 , . . . , rk1 }, and J0 r0 , r1 , Ji ri , ri1 , i 1, . . . , k, where
r0 0, rk1 T . Denote that Jio is the interior of Ji , i 0, 1, . . . , k. Let
⎧
⎫
x ∈ C Ji , RN , i 0, 1, . . . , k, ⎬
⎨
PC J, RN x : J −→ RN ,
⎩
lim xr exists for i 1, . . . , k⎭
r → ri
⎫
x ∈ C Jio , RN ,
⎬
.
PC1 J, RN x ∈ PC J, RN x r and lim− x r exist for i 0, 1, . . . , k⎭
⎩
rlim
→ r
r →r
⎧
⎨
i
1.6
i1
For any ur u1 r, . . . , uN r ∈ PCJ, RN , denote that |ui |0 sup{|ui r| | r ∈ J }.
i 2 1/2
, and PC1 J, RN Obviously, PCJ, RN is a Banach space with the norm u0 N
i1 |u |0 is a Banach space with the norm u1 u0 u 0 . In the following, PCJ, RN and
PC1 J, RN will be simply denoted by PC and PC1 , respectively. Denote that L1 L1 J, RN ,
T i
2 1/2
and the norm in L1 is uL1 N
.
i1 0 |u r|dr The study of differential equations and variational problems with variable exponent
conditions is a new and interesting topic. For the applied background on this kind of
problems we refer to 17–19. Many results have been obtained on this kind of problems,
Journal of Inequalities and Applications
3
for example, 20–35. If pr ≡ p a constant and qr ≡ q a constant, then 1.1 is the wellknown mean curvature system. Since problems with variable exponent growth conditions
are more complex than those with constant exponent growth conditions, many methods and
results for the latter are invalid for the former; for example, if Ω ⊂ Rn is a bounded domain,
the Rayleigh quotient
λpx inf
1,px
u∈W0
Ω\{0}
1/px |∇u|px dx
1/px |u|px dx
Ω
Ω
1.7
is zero in general, and only under some special conditions λpx > 0 see 25, but the fact
that λp > 0 is very important in the study of p-Laplacian problems.
In this paper, we investigate the existence of solutions for the prescribed variable
exponent mean curvature impulsive differential system initialized boundary value problems;
the proof of our main result is based upon Leray-Schauder’s degree. This paper was
motivated by 6, 13, 36.
Let N ≥ 1, then the function f : J × RN × RN → RN is assumed to be Caratheodory;
by this we mean that
i for almost every t ∈ J the function ft, ·, · is continuous,
ii for each x, y ∈ RN × RN the function f·, x, y is measurable on J,
iii for each R > 0 there is a βR ∈ L1 J, R such that, for almost every t ∈ J and every
x, y ∈ RN × RN with |x| ≤ R, |y| ≤ R, one has
f t, x, y ≤ βR t.
1.8
We say a function u : J → RN is a solution of 1.1 if u ∈ PC1 with ϕr, u absolutely
continuous on Jio , i 0, 1, . . . , k, which satisfies 1.1 a.e. on J.
This paper is divided into three sections; in the second section, we present some
preliminary. Finally, in the third section, we give the existence of solutions and nonnegative
solutions for system 1.1–1.4.
2. Preliminary
In this section, we will do some preparation.
Lemma 2.1 see 16. ϕ is a continuous function and satisfies the following.
i For any r ∈ J, ϕr, · is strictly monotone, that is,
ϕr, x1 − ϕr, x2 , x1 − x2 > 0,
for any x1 , x2 ∈ RN , x1 / x2 .
2.1
ii For any fixed r ∈ J, ϕr, · is a homeomorphism from RN to
E x ∈ RN | |x| < 1 .
2.2
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Journal of Inequalities and Applications
For any r ∈ J, denote by ϕ−1 r, · the inverse operator of ϕr, ·, then
−1/prqr
ϕ−1 r, x 1 − |x|qr
|x|1/pr−1 x,
for x ∈ E \ {0}, ϕ−1 r, 0 0.
2.3
Let one now consider the following simple problem:
ϕ r, u r hr,
2.4
r ∈ 0, T , r /
ri ,
with the following impulsive boundary value conditions:
lim ur − lim− uri ai ,
r → ri
i 1, . . . , k,
r → ri
lim ϕ r, u r − lim− ϕ r, u r bi ,
r → ri
r → ri
i 1, . . . , k,
2.5
u 0 u0 0,
where ai , bi ∈ RN , ki1 |bi | < 1; h ∈ L1 .
Obviously, u 0 0 implies that ϕ0, u 0 0. If u is a solution of 2.4 with 2.5, by
integrating 2.4 from 0 to r, then one finds that
bi ϕ r, u r r
∀r ∈ J .
htdt,
2.6
0
ri <r
Define a a1 , . . . , ak ∈ RkN , b b1 , . . . , bk ∈ RkN , and operator F : L1 → PC as
Fhr r
htdt,
2.7
∀h ∈ L1 .
0
From the definition of ϕ, one can see that
sup bi Fhr < 1.
r∈J r <r
2.8
i
Denote that
h ∈ L sup bi Fhr < 1 .
r∈J r <r
Db 1
2.9
i
By 2.6, one has
ur ri <r
−1
ai F ϕ
r,
ri <r
bi Fh
r,
∀r ∈ J.
2.10
Journal of Inequalities and Applications
5
Denote that W R2kN × L1 with the norm
wW k
k
|ai |
i1
|bi | hL1 ,
∀w a, b, h ∈ W,
2.11
i1
then W is a Banach space.
Let one define the nonlinear operator Kb : Db → PC1 as
−1
Kb hr F ϕ
r,
bi Fh
r,
∀r ∈ J.
2.12
ri <r
Lemma 2.2. The operator Kb is continuous and sends closed equiintegrable subsets of Db into
relatively compact sets in PC1 .
Proof. It is easy to check that Kb h· ∈ PC1 , for all h ∈ Db . Since
t,
Kb h t ϕ
bi Fh ,
−1
∀t ∈ J,
2.13
ri <t
it is easy to check that Kb is a continuous operator from Db to PC1 .
Let now U be a closed equiintegrable set in Db , then there exists η ∈ L1 , such that, for
any u ∈ U,
|ut| ≤ ηt
2.14
a.e. on J.
We want to show that Kb U ⊂ PC1 is a compact set.
Let {un } is a sequence in Kb U, then there exists a sequence {hn } ∈ U such that
un Kb hn . For any t1 , t2 ∈ J, we have that
t2
ηtdt.
|Fhn t1 − Fhn t2 | ≤ t1
2.15
Hence the sequence {Fhn } is uniformly bounded and equicontinuous. By AscoliArzela theorem, there exists a subsequence of {Fhn } which we rename the same that is
convergent in PC. Then the sequence
bi Fhn ϕ t, Kb hn t 2.16
ri <t
is convergent according to the norm in PC. Since
−1
Kb hn t F ϕ
t,
bi Fhn ri <t
t,
∀t ∈ J,
2.17
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Journal of Inequalities and Applications
according to the continuity of ϕ−1 , we can see that Kb hn is convergent in PC. Thus we
conclude that {un } is convergent in PC1 . This completes the proof.
We denote that Nf u : PC1 → L1 is the Nemytski operator associated to f defined by
Nf ur f r, ur, u r ,
2.18
a.e. on J.
Define K : PC1 → PC1 as
−1
Kur F ϕ
r,
Bi F Nf u
r,
∀r ∈ J,
2.19
ri <r
where Bi Bi limr → ri− ur, limr → ri− u r.
Lemma 2.3. u is a solution of 1.1–1.4 if and only if u is a solution of the following abstract
equation:
u
Ai Ku,
2.20
ri <r
where Ai Ai limr → ri− ur, limr → ri− u r, Bi Bi limr → ri− ur, and limr → ri− u r.
Proof. i If u is a solution of 1.1–1.4, since u 0 0 implies that ϕ0, u 0 0, by
integrating 1.1 from 0 to r, then we find that
Bi ϕ r, u r r
f t, u, u dt,
∀r ∈ J .
0
ri <r
2.21
Thus
u
Ai Ku.
2.22
ri <r
Hence u is a solution of 2.20.
ii If u is a solution of 2.20, then it is easy to see that 1.2 is satisfied. Let r 0, then
we have
u0 0.
2.23
From 2.20 we also have
Bi F Nf u r,
ϕ r, u r ∈ 0, T , r / ri ,
ri <r
ϕr, u f r, u, u ,
r ∈ 0, T , r /
ri .
2.24
2.25
Journal of Inequalities and Applications
7
From 2.24, we can see that 1.3 is satisfied. Let r 0, from 2.24, then we have
ϕ 0, u 0 0.
2.26
Since ϕr, x |x|pr−1 x/1 |x|qrpr 1/qr 0, we must have x 0; thus,
u 0 0.
2.27
Hence u is a solution of 1.1–1.4. This completes the proof.
3. Main Results and Proofs
In this section, we will apply Leray-Schauder’s degree to deal with the existence of solutions
for 1.1–1.4.
We assume that
H0 ki1 |Bi u, v| < 1/2, for all u, v ∈ RN × RN .
Theorem 3.1. If (H0 ) is satisfied, then 0 ∈ Ω is an open bounded set in PC1 such that the following
conditions hold.
10 For any u ∈ Ω, the mapping r → fr, u, u belongs to {v ∈ L1 | vL1 < 1/3}.
20 For each λ ∈ 0, 1, the problem
λf r, u, u ,
ϕ r, u
lim ur − lim− ur λAi
r → ri
r → ri
lim ur, lim− u r ,
r → ri−
lim ϕ r, u r − lim− ϕ r, u r λBi
r → ri
r ∈ 0, T , r /
ri ,
r → ri
3.1
r → ri
i 1, . . . , k,
lim ur, lim− u r ,
r → ri−
r → ri
i 1, . . . , k,
u 0 u0 0
has no solution on ∂Ω.
Then 1.1–1.4 has at least one solution on Ω.
Proof. Denote that
Ai Ai
lim ur, lim− u r ,
r → ri−
r → ri
Bi Bi
Denote that Ψu, λ : λ
ri <r
Ai Kλ u.
3.2
∀r ∈ J.
3.3
lim ur, lim− u r .
r → ri−
r → ri
For any λ ∈ 0, 1, define Kλ : PC1 → PC1 as
−1
λBi F λNf u
Kλ ur F ϕ r,
r,
ri <r
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Journal of Inequalities and Applications
We know that 1.1–1.4 has the same solutions of
u Ψu, 1 Ai K1 u.
ri <r
3.4
Since f is Caratheodory, it is easy to see that Nf · is continuous and sends bounded
sets into equiintegrable sets. According to Lemma 2.2, we can conclude that Ψ is compact
continuous on Ω for any λ ∈ 0, 1. We assume that for λ 1 3.4 does not have a solution on
∂Ω; otherwise, we complete the proof. Now from hypothesis 20 , it follows that 3.4 has no
solution for u,λ ∈ ∂Ω × 0, 1.
When λ 0, 3.1 is equivalent to the following usual problem:
0,
− ϕ r, u
u 0 u0 0,
3.5
where obviously 0 is the unique solution to this problem.
Since 0 ∈ Ω, we have proved that 3.4 has no solution u,λ on ∂Ω×0, 1, then we get
that, for each λ ∈ 0, 1, Leray-Schauder’s degree dLS I − Ψ·, λ, Ω, 0 is well defined. From
the homotopy invariant property of that degree, we have
dLS I − Ψu, 1, Ω, 0 dLS I − Ψu, 0, Ω, 0 1.
3.6
This completes the proof.
In the following, we will give an application of Theorem 3.1.
Denote that σ 4T/4T 1 and
Ωε j j u ∈ PC max u u < ε .
0
1≤j≤N
1
3.7
0
Obviously, Ωε is an open subset of PC1 .
Assume that
H1 fr, u, v δgr, u, v, where δ is a positive parameter, and g is Caratheodory.
H2 ki1 |Ai u, v| ≤ σ/2ε, ki1 |Bi u, v| ≤ {min|ε/4T 1|pr /21|Nε|qrpr 1/qr ,
r∈I
1/2}, for all u, v ∈ RN × RN .
Theorem 3.2. If H1 -H2 are satisfied, then problem 1.1–1.4 has at least one solution on Ωε ,
when positive parameter δ is small enough.
Proof. Let one consider the problem
u Ψu, λ λ
ri <r
where Kλ · is defined in 3.3.
Ai Kλ u,
3.8
Journal of Inequalities and Applications
9
Obviously, u is a solution of 1.1–1.4 if and only if u is a solution of the abstract
equation 3.8 when λ 1. We only need to prove that the conditions of Theorem 3.1 are
satisfied.
10 When positive parameter δ is small enough, for any u ∈ Ωε , we can see that the
mapping r → δgr, u, u belongs to {u ∈ L1 | uL1 < 1/3}.
20 We shall prove that for each λ ∈ 0, 1 the problem
λf r, u, u ,
ϕ r, u
r ∈ 0, T , r /
ri ,
lim ur − lim− ur λAi
r → ri
r → ri
lim ur, lim− u r ,
r → ri−
lim ϕ r, u r − lim− ϕ r, u r λBi
r → ri
r → ri
3.9
r → ri
i 1, . . . , k,
lim ur, lim− u r ,
r → ri−
r → ri
i 1, . . . , k,
u 0 u0 0
has no solution on ∂Ωε .
If it is false, then there exists a λ ∈ 0, 1 and u ∈ ∂Ωε is a solution of 3.8. Then there
exists an j ∈ {1, . . . , N} such that |uj |0 |uj |0 ε.
i Suppose that |uj |0 ≥ σε, then |uj |0 ≤ 1 − σε. For any r ∈ J, since u0 0,
according to H2 and 1.2, we have
r j j
j
j
u tdt Ai u r u r − u 0 0
0<r <r
i
T ≤ uj tdt |Ai |
0
≤
T
0<ri <r
1 − σεdr
0
k
3.10
|Ai |
i1
σ
3σ
σ
ε ε
ε.
4
2
4
≤
It is a contradiction.
ii Suppose that |uj |0 < σε, 1−σε < |uj |0 ≤ ε. This implies that |uj r∗ | > 1−σε 1/4T 1ε for some r∗ ∈ J.
Denote that
|u |pr−1 uj r
ϕ r, u r 1/qr .
1 |u |qrpr
j
3.11
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Journal of Inequalities and Applications
Since u 0 0, we have
r∗
ϕj r∗ , u r∗ λ
0
j
f j r, u, u dr λ
Bi .
3.12
0<ri <r∗
According to H1 -H2 , when positive parameter δ is small enough, we have
r∗ |ε/4T 1|pr∗ j
j
j
≤
λ
λ
≤
,
u
B
r
r,
u,
u
r
dr
f
ϕ
∗
∗
1/qr∗ 0<r <r i 0
i
∗
1 |Nε|qr∗ pr∗ ≤δ
T
0
βNε rdr
k
i1
|ε/4T 1|pr∗ |Bi | < 1/qr∗ .
qr∗ pr∗ 1 |Nε|
3.13
It is a contradiction.
Summarizing this argument, for each λ ∈ 0, 1, the problem 3.8 with 1.4 has no
solution on ∂Ωε .
Since 0 ∈ Ωε and 0 is the unique solution of u Ψu, 0, then the Leray-Schauder’s
degree
0.
dLS I − Ψ·, 0, Ω, 0 1 /
3.14
This completes the proof.
In the following, we will discuss the existence of nonnegative solutions of 1.1–1.4.
For any x {x1 , . . . , xN } ∈ RN , the notation x ≥ 0 x > 0 means that xl ≥ 0 xl > 0 for every
l ∈ {1, . . . , N}.
Assume the following
H3 fr, u, v δgr, u, v, where δ is a positive parameter, and
gr, u, v τr |u|q1 r−1 u μr|v|q2 r−1 v γr,
3.15
where q1 , q2 ∈ CJ, R, 0 ≤ q1 r, and 0 ≤ q2 r, for all r ∈ J.
j
j
H4 Ai x, yyj ≥ 0, and Bi x, yyj ≥ 0, for all x, y ∈ RN , i 1, . . . , k, j 1, . . . , N.
H5 μ, τ ∈ CJ, R .
H6 γ γ 1 , . . . , γ N ∈ CJ, RN satisfies γ0 > 0,
t
0
γsds ≥ 0, for all t ∈ 0, T .
Theorem 3.3. If H2 –H6 are satisfied, then the problem 1.1–1.4 has a nonnegative solution,
when positive parameter δ is small enough.
Journal of Inequalities and Applications
11
Proof. From Theorem 3.2, we can get the existence of solutions of 1.1–1.4. If u is a solution
of 1.1–1.4, according to 1.4 and H6 , then we have
f 0, u0, u 0 δγ0 > 0.
3.16
Obviously
ϕ r, u r r q r−1 δ τr |u|q1 r−1 u μru 2
u γr ds,
∀r ∈ 0, r1 .
3.17
0
When r → 0 , we have
q r−1 τr |u|q1 r−1 u μru 2
u γr > 0,
3.18
then we can see that there exists a ξ ∈ 0, r1 such that ϕr, u r > 0 when r ∈ 0, ξ. Thus
u r > 0 for any r ∈ 0, ξ. Thus ur is increasing in 0, ξ, that is, uη2 ≥ uη1 for any
η1 , η2 ∈ 0, ξ with η1 < η2 . Since u0 0, it is easy to see that ur > 0 for any r ∈ 0, ξ. From
3.17 and H5 , we can easily see that
ur > 0,
u r > 0,
lim ur > 0,
r → r1−
∀r ∈ 0, r1 ,
lim u r > 0.
3.19
r → r1−
From H4 , we can see that
lim ur > 0,
r → r1
lim u r > 0.
r → r1
3.20
Similarly, we can see that
ur > 0,
u r > 0,
∀r ∈ r1 , r2 .
3.21
∀r ∈ J .
3.22
Repeating the step, we can see that
ur > 0,
u r > 0,
Hence u is nonnegative. This completes the proof.
Acknowledgments
This paper is partly supported by the National Science Foundation of China 10701066,
10926075 and 10971087, China Postdoctoral Science Foundation funded project
20090460969, the Natural Science Foundation of Henan Education Committee 2008-75565, and the Natural Science Foundation of Jiangsu Education Committee 08KJD110007.
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Journal of Inequalities and Applications
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